Sarah Ferguson is accused of violating the privacy of orphans she filmed with a hidden camera outside Ankara [AFP]

Turkish prosecutors have charged a member of the British royal family for secretly filming a documentary critical of conditions in Turkish orphanages in 2008.

The Anatolia news agency said Sarah Ferguson, the Duchess of York, was accused of violating the privacy of five children when she filmed with a hidden camera at an orphanage outside Ankara.

Britain has already rejected a 2009 request from Ankara for Ferguson's extradition.

A spokesman for Ferguson said: "The Duchess of York has fully co-operated with both the Turkish and British authorities at all times on this issue.

"British ministers refused to accede to the further request for legal assistance from Turkey so from a UK perspective we have been told by the Home Office the case is closed.

"We were told the reasons for refusal were that the minister considered that to provide the assistance requested would have been likely to prejudice the sovereignty, security, ordre public or other essential interests of the United Kingdom.

"The action today (Thursday) reported by the Turkish authorities is news to all."

A British Foreign Office spokeswoman said it was not government practice to comment on individual judicial processes, although it expected "high legal and judicial standards to be observed".

"It would be premature and inappropriate to speculate on possible outcomes at this stage," added the ministry.

Ferguson married Prince Andrew, second son of Queen Elizabeth II, in 1986 but the couple divorced in 1996.

The duchess has been involved in a series of embarrassing episodes which resulted in her being snubbed for last year's wedding of Prince William and Catherine Middleton.

In 1992, while still married to Andrew, she was photographed sunbathing while apparently having her toes sucked by US financial manager John Bryan.

Ferguson, who has recently struggled with her personal finances, was caught by undercover News of the World journalist Mazher Mahmoud in 2010 offering access to Prince Andrew for £500,000 ($770,000).

The documentary, screened on Britain's ITV television channel in November 2008, depicted disturbing scenes at the orphanage for handicapped children, including one where a child is seen encased in a wooden box.

Turkish prosecutors are seeking a prison term of between seven and a maximum of more than 22 years. No date has been set for any trial.

Ankara accuses Ferguson of malice and trying to stain Turkey's reputation as the country tries to gain entry into the European Union.